The present invention relates to an operating theatre lamp comprising a housing provided at the bottom with a light outlet opening, a light source is centrally arranged in the housing and emits light all around towards a main ring concave reflector mounted in the housing. The main reflector deflects the incident light rays towards the light outlet opening and concentrates these light rays on a site of operation. At least one auxiliary ring reflector is provided between the light source and the main reflector outside of the light rays propagating from the light source to the main reflector. The auxiliary reflector receives the light rays which would normally pass to the side of the main reflector and deflects them toward locations of the main reflector at which they are deflected toward the site of operation.
Operating theatre lamps serve to illuminate the site of an operation opened by a surgeon in a patient. In this case it is important that the illumination be bright and regular, also permitting the surgeon to recognize minute tissular differences owing to a high colour fidelity and ensuring a far-reaching absence of shadows. The light rays must arrive onto the site of operation not only perpendicularly, but they must also include at least in part important components coming from the side in order that largely vertical walls of deep wounds can also be sufficiently illuminated. The main reflectors of such operating theatre lamps are therefore designed in such a way that they emit a mixture of light falling practically perpendicular onto the site of operation with obliquely falling light. Far-reaching absence of shadows signifies that apparatus or the hands and the head of the surgeon brought into the light bundle do not give rise to shadows in the site of operation which would disturb the observation.
In the prior art one can find one-eyed lamps operating with a large parabolic annular reflector, in particular a polygonal reflector, as well as so-called multi-eyed lamps which comprise several individual lamps arranged on the underside of the lamp body. The invention is concerned with one-eyed operating theatre lamps, wherein the central light source can nevertheless also be realized by means of two lamps or more in close propinquity. The light source lies at the center of the main reflector, from which the light rays extend all around in straight lines toward the main reflector.
It is however, also possible that one or several light sources emit the light from above onto a ring reflector concentrically arranged in the housing, this reflector deflects the light rays laterally toward the main reflector (DE-OS 36 33 609; GB-PS 1 517 357). Further, an operating theatre lamp which ensures an illumination of a site of operation practically without cast shadows is already known (GB-PS 825 638), in which the normally lost light rays of the light source are deflected toward the main reflector by means of an auxiliary reflector arranged above the light rays which extend toward the main reflector. The advantage of providing an upper auxiliary reflector resides in that the housing can be made narrower in vertical direction, i.e. more compact than when using a main reflector having a greater extension. A problem with such a configuration is a larger distance from the apparent interception point of the imaginary extensions of the rays of the auxiliary reflector with the center of the main reflector. In the known solution it is therefore not possible to simultaneously overlay direct lamp light and light coming from the auxiliary reflector in regions of the main reflector. Therefore it is not possible to achieve the required compact construction with the required absence of cast shadows and regular illumination.
The object of the invention is to realize a further operating theatre lamp of the kind mentioned at the beginning.
In order to solve this problem, the invention provides that the auxiliary reflector(s) arranged above and/or below the light rays propagating from the light source to the main reflector. The auxiliary reflector(s) deflect the incoming light from the light source substantially back toward the light source or past the latter to the region of the main reflector which is at least substantially diametrically oppositely disposed on the opposite side of the light source.
Thus, according to the invention, the light which would otherwise be lost is not deflected to the side of the main reflector on which the reflecting location of the auxiliary reflector is placed, but precisely to the diametrically opposite side. This firstly provides the advantage that the auxiliary reflector or reflectors are not impinged on under a flat angle but at least approximately perpendicular by the light of the light source, such that despite the interception of larger angular ranges of emitted light the width of the auxiliary reflector or reflectors can be kept low. Further, by appropriate inclination of the reflecting regions of the auxiliary reflectors, the reflected light can be deflected in this manner in an ideal manner onto such regions of the main reflector from which this light not only arrives on the site of operation but also illuminates the latter in a regular manner.
In order to keep the width of the auxiliary reflector or reflectors as low as possible, the auxiliary reflectors are provided as close as possible to the light source, under consideration of the heating by the light source, and/or substantially on the same radius as a filter arranged all around the light source.
When appropriately dimensioning the main reflector and the auxiliary reflectors it is possible to achieve that the light lost in the site of operation because of a cut-away region of the main reflector is precisely completed again at the same place by the light intercepted by the auxiliary reflector. Therefore, despite the saving of surfaces at the outer periphery of the main reflector one obtains in a far-reaching manner the same illumination of the site of operation as with a larger main reflector.
According to a further embodiment a filter cylinder held on the housing by means of upper and lower fixtures is arranged around the light source. The filter cylinder is located in the radiation path to the main reflector and the auxiliary reflector or reflectors are secured at the top and/or the bottom on the fixtures.
Owing to these features, it is also possible to use for the mounting of the auxiliary reflectors the same mountings which are provided for the filter. The filter cylinder generally serves to filter the heat issuing from the light source and also optionally the UV radiation.
A further important affect is that the radially further outwardly-lying regions of the main reflector, at which prevails otherwise the lowest light intensity because of the relatively important distance from the light source, are additionally subjected with light, which leads to a constant illumination of the site of operation on shadowing out by persons.
In order to be able to also reduce the diameter of the main reflector, it is advantageous to provide both an upper and a lower auxiliary reflector. In this way it is possible to cut away the lower regions located radially mostly outwardly in a conventional main reflector, such that a lower diameter of the lamp is achieved. The light which is lost in this manner is deflected by the lower auxiliary reflector toward radially further inwardly disposed regions of the main reflector, in particular in its upper region, such that this light is not lost.
Owing to the features of the invention it is thus possible to reduce both the height and the diameter of the operation theatre lamp without reducing illumination of the site of operation. The diameter reduction is indeed comparably low but results in the laminar air flow usually provided in operation rooms from the top toward the bottom is significantly less affected than by a known operation theatre lamp having a somewhat larger diameter with a same light intensity and a same illumination of the site of operation. Indeed, the cross-section of the lamp reduces as a function of the square of the radius.